The present invention relates to dental floss and, more particularly, to a dental floss having a low density.
Use of dental floss remains one of the most recommended ways of preventing and controlling gum disease. Several types of floss are currently known and used. These flosses are made of materials such as nylon, polyethylene, ultra-high molecular weight polyethylene, polytetrafluoroethylene (PTFE), and expanded PTFE (ePTFE). Of these, ePTFE floss, and particularly monofilament ePTFE floss, is particularly preferred, in part because of its inherently low friction properties which allow it to slide between teeth more easily.
Certain characteristics are typically considered desirable for dental floss. First, the floss should be abrasion resistant such that it does not shred, fray, or otherwise break during use when passed between a user""s teeth. In order to be used effectively, the dental floss should also be grippable; that is, able to be grasped by a user""s hands or other device for manipulation between the teeth without slipping in the hands or other device. Several attempts have been made at making PTFE flosses more easily grippable. As discussed in U.S. Pat. No. 5,518,012 to Dolan, et al., for example, a waxed coating may be placed over the PTFE fiber in order to make the floss more grippable. In U.S. Pat. No. 5,911,228 to Curtis, et al, a solid additive is incorporated within the PTFE fiber structure in order to make the fiber grippable without the need for any coating. A grippable PTFE floss that did not require the use of either a coating on the fiber or additives within the fiber in order to make it grippable, would be desirable.
A dental floss should also have the subjective advantage of having a good xe2x80x9cfeelxe2x80x9d for the user. The feel includes the overall handling characteristics of the fiber as well as the perceived effect of the fiber in a user""s mouth as it cleans the teeth. Desirably, a PTFE dental floss should be soft and conformable to slide comfortably between a user""s teeth, while at the same time providing a scrubbing or cleaning sensation for the user when manipulated under the gums. The floss should have a soft feel to the hands and a rough feel in the mouth.
A PTFE floss having all of these advantages and characteristics would be desirable.
The present invention provides a dental floss comprising a fiber having a denier between 100 and 3,500 and having a density of less than about 0.8 g/cc, with additional ranges for alternative embodiments of less than about 0.7 g/cc, less than about 0.6 g/cc, less than about 0.5 g/cc, less than about 0.4 g/cc, less than about 0.3 g/cc, and less than about 0.2 g/cc. The floss has a strength suitable for use as a dental floss, typically greater than about 1.5 lbs, with additional ranges for alternative embodiments of greater than about 2 lbs, greater than about 2.5 lbs, greater than about 3 lbs, greater than about 5 lbs, greater than about 7.5 lbs, and greater than about 10 lbs. The floss may be a hollow fiber with any desired cross-section, such as substantially elliptical or rectangular. The floss is also abrasion resistant, having an average abrasion break strength in various embodiments of greater than 2.8xc3x9710xe2x88x923 lbs. per denier, greater than 3.0xc3x9710xe2x88x923 lbs. per denier, greater than 4.0xc3x9710xe2x88x923 lbs. per denier, greater than 5.0xc3x9710xe2x88x923 lbs. per denier, or greater than 6.0xc3x9710xe2x88x923 lbs. per denier. The inventive floss has increased surface roughness with an average roughness greater than about 0.3 microns (preferably about 1.3 microns), a root mean square roughness of greater than about 0.35 microns (preferably about 1.6 microns), and a peak to valley distance of greater than about 1.7 microns (preferably about 6.3 microns). The dental floss may be any material suitable for a floss, and porous PTFE is preferred, particularly expanded PTFE. There may be a plurality of fibers in the floss, each with the same or different composition. The floss may include a filler.
In another aspect, the present invention provides a method of making a dental floss including the steps of providing a PTFE resin, extruding said resin to form an extrudate, and expanding the extrudate into a fiber having the properties presented above. The extrusion is performed in the preferred embodiment with a mandrel in the extruder. Reduction ratios in the extruder in various embodiments may be greater than 150 to 1, greater than 200 to 1, greater than 250 to 1, greater than 300 to 1, or greater than 500 to 1. The extrudate is heated during expansion by non-contact heating such that the extrudate does not touch the heat source during the process.
In still another aspect, the present invention provides a filament having the properties and composition presented above.
In still further aspects, the present invention provides an improved sewing thread, a fiber for weaving, and a filament for structures in bearing and bushing applications.